2. Up-to-5 Year Old Casualties during Use/Non-use of CRS
2.1. Analyzed Accidents

  To develop effective measures for reducing injuries to vehicle occupants, it is important to examine individual accident cases and determine relationships between injuries, inflicting objects, impact speed and so on. Since 1993, ITARDA has conducted in-depth investigations of the accidents that occurred within the Tsukuba/Tsuchiura City district where the Institute is located.

  Using the Micro Investigation Database (hereafter referred as "Micro Data") obtained from these case studies between 1993 and 1999, analysis was carried out on chest injuries and the inflicting objects in the passenger compartment. As in the Macro Data study, the Micro Data was aimed at frontal collision vehicles in the vehicle-alone and vehicle-to-vehicle configurations.

  To obtained the maximum number of case studies involving older drivers, 6 ordinary passenger cars, 2 light passenger cars, 2 ordinary trucks, and 2 light trucks were selected from the case studies. Accordingly a total of 12 older drivers came under the examination.

 
2.2. Chest Injury Due to Seat Belt

  The drivers' age, injury types, AIS*5, inflicting objects, and vehicle categories are shown in Table 1. In the cases where the seat belt was not used and the airbag did not deploy or was not equipped, all the chest injuries were ascribable to the steering wheel.

  Nevertheless, where the seat belt was used but the airbag did not deploy or was not equipped, about half of the chest injuries were judged to have been caused by the seat belt. Where the seat belt was used and the airbag deployed, practically all the chest injuries, serious or slight, were attributed to the seat belt rather than the steering wheel.


Table 1 Micro Data on Chest Injuries of Older Drivers

Note 5: Examples of AIS (Abbreviated Injury Scale) for chest injury
AIS1
 Bruising, fricative scar on skin, or a broken rib without lung damage
AIS2
 2 or 3 broken ribs without lung damage
AIS3
 A damaged lung or 3 or more broken ribs on one side
AIS4
 Damaged lungs, 3 or more broken ribs on both sides, or minor artery damage
AIS5
 Major lung damage, major artery damage, or lacerated ventricle/atrium of heart
AIS6
 Ruptured ventricle of heart

 
2.3. Fracturing of Ribs by Seat Belt
  Introduced here is the example of an older driver who received a serious injury rated AIS 3 to the chest, although the airbag deployed. The accident, a head-on collision, occurred in an intersection area between an ordinary passenger car (Car A) and a light passenger car (Car B), as illustrated in Figure 9.

 Fig. 9 Accident configuration of Cars A and B

 

  The older driver, 68 years old, 168 cm tall and plump, was driving Car B. The crash velocity was estimated at approximately 30 km/h for Car B and 25 km/h for Car A. Although the older driver wore the seat belt and the airbag deployed at the crash, the older driver sustained a serious AIS-3 injury with four broken ribs (4th to 7th ribs).

  As shown in Figure 10, the ribs was fractured along the line of the shoulder seat belt and it was concluded that the fracture of the ribs was due to the shoulder seat belt. Contusion to a lung, rated AIS 3, was also observed underneath the broken ribs. In addition it was believed that the steering wheel was also responsible for the damage to the ribs and the lung.

 

 Fig. 10 Injuries to the older driver of Car B

  Due to the fact that the steering wheel of Car B was deformed, it was theorized that first the ribs were fractured by the seat belt at the head-on collision, which was then accompanied by contusion to the lung in the broken rib area as the chest hit the steering wheel through the deployed airbag. The primary reason why the chest came into contact with the steering wheel was the excessively forward positioning of the driver's seat. The absence of injury in the head and face was regarded as the result of protection by the deployed airbag.

  Car B also had a 15-year-old girl in the front passenger seat. She did not wear the seat belt, while her seat lacked an airbag. As a result she hit the front windshield in the head and the lower instrument panel in the legs, but her injuries were rated slight. The 28-year-old male driver of Car A, which in its right turn crashed head-on with Car B, received no injury thanks to protection by the seat belt.

UP
Institute for Traffic Accident Research and Data Analysis (ITARDA)